CA2279628A1

CA2279628A1 - Double pressing carbon fiber

Info

Publication number: CA2279628A1
Application number: CA002279628A
Authority: CA
Inventors: Michael Quddus
Original assignee: Sport Maska Inc
Current assignee: Sport Maska Inc
Priority date: 1999-08-04
Filing date: 1999-08-04
Publication date: 2001-02-04
Also published as: US6696001B1; EP1086724A1

Description

., 1 DOUBLE PRESSING CARBON FIBER
Field of the invention The present invention relates to a hockey stick shaft having fiberglass and graphite reinforcement and to a method of making the same.
Backs~raund of the invention The following is a comparison of existing techniques for reinforcing a hockey stick, and a brief description of the application of fiberglass to reinforce a hockey stick, and contrasted with the present invention.
Comparison of Carbon Fiber Application with Existing Technology Carbon Fiber Application witf~ PuU-Pressed V'myl Ester vs Pull-Preen Polymer 1. Graphite rovings do not absorb polyester resin.
A carbon/polyester matrix does not benefit fully from the higher modulus of elasticity of graphite because the filaments remain dry. Break this type of laminate and you will see the rovings will remain intact, proving that they are not an integral part of the matrix. This means they are not contributing as much to the rigidity of the finished laminate. In addition, the bond between the graphite and the wood core is very poor, so only a small quantity can be used, compared to the amount of fiberglass.
This reduces the overall contribution of the carbon.

2. Strength to weight ratio of finished products.
Using the same core, a stick made using polyester laminates will weigh 700g for a 50 KP (kilo-poundal) shaft, and will be limited to 2 12K graphite rovings per laminate, mixed with 16 fiberglass rovings. A vinyl ester laminated stick will weigh 600g for the same stiffness, using 5 24K
graphite rovings per laminate, or ten times more carbon content, with 8 fiberglass rovings. Furthermore, the energy transfer to the puck during slapshots will increase with the amount of carbon used.

3. Placement of rovings The final alignment guides shown in figure 15, page 18, ensure that there is fiberglass filling the corners of the shaft. The tradition polyester process does not control the position of individual rovings, treating the entire group as a unit. There is increased risk of having nothing but resin in the slash resistance grooves (see figure 2, page 4). Without fibers, the resin will chip and crack upon impact. In addition, there is no control over the distribution of rovings over the laminate cross section.

4. Finished Shaft Dimensions For the sample stick described in no. 2 above, the average laminate thickness would be 0.040" with polyester, versus 0.0025" for vinyl ester. The finished shaft with polyester is 0.83" thick versus 0.79" with vinyl ester. The industry trend is towards a demand for slimmer shafts.
Small resin pots and non-uniform laminates.
Since the polyester resin is not refrigerated, the size of the bath is limited. On a press with two lengths of sticks, one portion of the laminate will have soaked in resin during the entire pressing cycle or longer.
' The rest of will simply pass through, for an immersion time of a few seconds. The weight percent of resin in the soaked section is much higher, and cannot be removed through wringing. So a portion of the laminate is thicker and heavier than the rest. The vinyl ester process uses a refrigerated resin bath, which allows for resin bath as long as the total laminate length to be pressed. All rovings in the laminate will receive a uniform wet-out time, promoting an even thickness and weight percent of resin.

" 3 Polyester viscosity control additives Fillers such as micro-bubbles are added to increase the viscosity of polyester. This done to reduce leakage of resin from the moulds, which must be scraped off later. The reduces the rate of resin penetration in the rovings, even for fiberglass. In the vinyl ester process, there are no fillers, so that wetting is improved, and more excess resin is removed during wringing. This reduces the laminate weight.
Carbon Fiber Application wilff Pressed V'uryl Esher versus Epoxy laminates

5. Epoxy laminates have carbon distributed throughout the width of the product. This means graphite rovings can exist in the corners, which greatly reduces the slash resistance of the stick. The use of final alignment guides in the carbon fiber application with vinyl ester ensures that the carbon is in the center of the laminate, safe from slashing contact.
Dole Pn~sMg versus Single Pre~ng Production Capacity The double pressing system produces twice as many shafts per unit time as the single pressing technology.
Laminate-to-core bond quality In single pressing, the first laminate is glued by applying pressure to the unlaminated side of the core. The load is transferred through the core to the laminate, which is trapped between the core and the mould surtace. This means that one side of the core is pressed by a metal plate before it is glued to a laminate.
The pores of the wood on this side will be smoothed by this, reducing the bond quality when the core is eventually turned over. The result is that one laminate will have a better bond than the other. This can be proven by peeling off cold pressings, and verifying the amount of wood that comes off in the process. In contrast, double pressing treats both sides symmetrically, so that bond quality is equal for the top and bottom laminates.

Cooling Stresses In single pressing, one side can be allowed to cool before the other is pressed. The contraction of the laminate will curve the shaft to one side. Double pressing guarantees that both sides cool simultaneously.
Any stresses induced by the cooling laminates are evenly distributed on both sides.
SUMMARY OF THE INVENTION
The present invention concerns a hockey stick shaft having two opposed surfaces, each of the surfaces being provided with a fiberglass roving reinforcement along each opposite edge and a graphite roving reinforcement fiber between the two fiberglass roving means.
The present invention also concerns a method for making such a hockey stick shaft by a double pressing process, and an apparatus for making the same.
DESCRIPTION OF A PREFERRED EMBODIMENT
The following is a description of a preferred embodiment of the method for double pressing a shaft, and of a preferred apparatus for carrying out the same.

6 Fibers Fiberglass rovings are type 30TM, composed of continuous M-type glass filaments having no mechanical twist, with a forming agent designed for vinyl ester or polyester resins. The package as supplied feeds from the center. Choose ravings having fast wet-out, zero catenary, and excellent runnability.
Carbon fiber ravings are type 34 composed of continuous filaments, with a surface treatment compatible with vinyl ester resin. The package as supplied feeds from the perimeter of the spool.
Resin For the resin pot configuration listed in this text, obtain 227kg of vinyl resin. Measure 3%
of this mass in dibenzoyl peroxide (AKZOTM CADOX BTW 55) paste, as well as 3%
tertiary butyl perbenzoate (AKZOTM Trigonox-C) liquid. Do not mix immediately:
the percentage of each catalyst is adjusted between 0.3% and 3% depending on the desired gel time. (See Adjusting for Gel Time).
Vscosity Range (Brookfield cps) = 450-600 vinyl ester, 1500-2000 polyester.
Higher numbers make wringing out the excess difficult, increases friction, and cause resin to overflow the bath walls during the fiber pull stroke.

.. 7 Shaft Core The core has the following geometric profile (see figure 2):
The eight 0.11" x 0.370"
1.1950 grooves on the top and 0.1500 0.0300 bottom improve the bond 0.0150 between the laminates 0.0950 J and the core. The 0.115"
0.7490 x 0.15" grooves at each comer are filled with the resiNfiberglass matrix, ~ Figure 2: Cross-section of senior core (inches) providing slash resistance and increasing the stiffiess in the x-axis.
Core materials must be able withstand 190 psi with less than 2.5% plastic deformation at 145°C. Four quarter aspen wood is a typical example. In this case, humidity must be less than 6%. Otherwise the core will shrink as the water evaporates during the press cycle.
Processing aids:
Mould release agent: Proprietary complex mixture of primary, secondary fatty amines with copolyemers of organic phosphates esters and fatty acids. Applied directly to the mould, preferably before heating the mould, the vapors are unpleasant. (AXEL MoIdWiz INT-PUL24).

Equipment Resin and Catalyst Mixer (see Figure 3: Resin Mixer).
RESIN MIxER
ISION PR~OF'M~TOR
SE AC, 9 HP
.PM

SUPPORT
IRT FAR
:OL PANEL
IDARD DRUM
2 x 1'-ll2 TUBES
Figure 3: Resin mixing apparatus (propeller not shown).
Insert a three blade outboard propeller with 10" outer diameter close to the bottom of a standard drum. Pour the resin in first, followed by the correct percentages of each catalyst (see Adjusting for Gel Time). Spin the propeller at 50-100rpm for 20 minutes.
Both polyester and vinyl ester resins contain styrene. Use a face mask with organic vapor filters to reduce the quantity of vapors you inhale.

Procedure Filling the Creels Guide all rovings individually from the storage rack to the resin bath with ceramic or plastic bushings. (See figure 4) Rovings do not cross paths. Each path is as straight as possible.
For sticks with graphite, there are 4-10 fiberglass rovings per laminate.
Sticks have 10-18 fiberglass ravings per laminate when this is the only reinforcement.
CREEL FOR CARIiCN SP~LS
CARBl7N ROV1NG~
CARBON ROVINGS
CREEL FOR CARB(YJ SPOOL
FIBERGLASS
-'~- CARHl7N GROUPING PLHTE

VRl NGER
eD ~
SEPARATl7R eFIHERGLRSS ,~ ~ ~~PRO~ING~~
WETTED RCIVINGS ~ Ilff/YY~
~ CP1RBDN fNGS
WpT FIBER GUIDE p INNER AA
JACKET R
BROKEN
J
~ Figure 4: Guiding the rovings from the creel to the bath.

Fiberglass Place fiberglass ravings higher than the top of the resin pot so that gravity compensates for dynamic fiction. Each spool is centred beneath its first guide. (See figure 5).
s~a~
FIBERO
~ Figure 5: Fiberglass spool in creel with roving feeding from the center, Carbon Fiber Center guides over each spool, at a height that ensures no rubbing with the roving as it unravels. (See figure 6). Place carbon fiber spools higher than the fiberglass spools, to ~ Figure 6: Carbon fiber spools in creel.

take advantage of the extra potential energy. (See figure 4). Unlike fiberglass, graphite rovings have medium runnability, which makes them more susceptible to fraying and fuzz.
When these particles fall into the resin bath in sufficient quantities, the viscosity increases.
There are 2-12 carbon fiber rovings per laminate.
Dry Fiber Guidance: From Creel to Bath Upon leaving the creel, group the rovings together in anticipation of their positions within the resin bath. Figure 4 shows 32 fiberglass and 20 carbon spools, with the ravings for some of them threaded from the spool perimeter or center, grouped together through a series of plates, reoriented to enter the resin bath, and finally guided to the wringer. The bath is drawn as a broken section, to reveal the wet fiber guide.
When threading a roving through this route, masking tape is wrapped around the end of the roving to form a rigid cylinder. This is easier to guide through the rest of the trajectory.
The objectives are: to prevent the groups from crossing each other, make it easy for the operator to identify any roving in each group, and to limit the friction incurred by the rovings touching the guides.
The fiberglass rovings are passed through the group hole which produces the most gradual transition from its initial trajectory to the resin bath. (See Figure

7). For example, a fiberglass spool positioned on the uppermost creel level, close to the wringer, will be threaded through a hole in group 1.

~ Figure 7: Initial grouping fiberglass rovings in plastic guide plate (Four rovings per group).
Groups 1,2,3,4,7,8,9,10 have four fiberglass rovings each. The plastic guide plate shown in figure 7 prevents them from crossing or rubbing against each other as the enter the final guide plate before the resin bath, as shown in figure 8. Groups 5,6,11 and 12 shown are ~ Figure 8: Graphite and fiberglass roving groups in the last guide plate before entering the resin bath.

for graphite rovings.
Since the graphite spools are placed highest in the creel structure, there is a separate guide plate for the initial grouping of these rovings, as shown in figure 9.
For simplicity, the roving groups 5 and 11 are shown. Each contains five individual rovings.
/~~
~ ~'z ~ ~ -_ ~ ~ ~ ~ ~ ~~. i ~ ~
~ Figure 9: Graphite rovings grouped together in plastic guide plate.

Wet Fiber guides Within the resin bath, four guides maintain the integrity of the roving groups. After passing through the final roving guide plate, roving groups 1-12 pass into the wet fiber guide. (See figures 10 and 11). Groups 1-4 are indicated in the bottom row the guide.
Resin is contained by the inner liner, with water circulating the length of the bath between the inner liner and outer jacket.
"'L'~- E tNAL R V I
GLASS
JACKER-I ~ RNVIN ' 9~~' f ~~ f GUIDE P AT
~ Figure 10: Path of the rovings into the resin with broken section of bath.

Identification of the Resin Bath and Flber Wrinsing System As the rovings are pulled through the press, they soak in a resin bath, then pass through a wringing system to remove the excess resin. The resin bath soaks carbon and glass fibers with a resin mixture for the duration of the pressing cycle. The weight % of resin over the entire length of the laminate is constant: All the fibers over the length of the laminates have the same immersion time.
The resin container is of sufficient depth to contain the gradient caused by movement of the rovings during pulling.
Preparing the resin bath and wringing system.
The cooling system must be in operation. The wall temperature of the bath is 5-10°C. The temperature of the resin is controlled as follows: A chill-water refrigeration unit maintains the temperature of a water reservoir. A pump delivers water to an open bath (see figure 11 ), with another pump sending it back to the reservoir. A liner containing resin is ~ Figure 11: Exploded view of refrigerated resin bath assembly.

immersed in this bath. Flowing water enters the open bath, which now acts a jacket, cools the liner, and thus the resin within. Manual balancing valves control the flow rate, and thus the heat transfer rate. Reducing the temperature slows down the catalytic reaction of the resin mixture and increases the viscosity. Employing additives to alter viscosity would reduce the penetration of resin into the rovings.
Verify that no water is leaking into the bath, and that condensation on the walls and floor of the bath is wiped off. It will not mix with the resin, but its presence on the hot mould surface will produce uncooked resin in that area, due to the energy consumed by boiling and evaporation. In addition, all debris is removed from the bath before filling. The bath is not made of copper, or aluminum, as these will react with the resin over the long term.
There are 11 tempered black-oxide blades for each pair of upper and lower laminates: flue touch the wetted rovings from above, six from below. (See figure 12 below).
These wring excess resin from the wetted fibers as they pass over and under the blades.
UPPER LAMINATE
~ WRINGING SYSTEM- SUPPORT PLATE
BLADE HOLDER
FINA\
ALIGNMEN ,T
GUIDE ~ WET ROVING SEPARATOR
LOWER LAMINATE WET CARBON
ROVING
TEMPERED BLADE
INNER LfNER (CONTAINS RESIN> FIBERGALSS
ROVING
WET ROVING GUIDE
OUTER JACKET
(CONTAINS COOLING WATER) ~ Figure 12: Isometric view of wringing and alignment system.

.. . 17 Separators maintain the integrity of the roving groups at the entry and exit of the wringing process. Roving groups should be confined to these guides. If they are not, the separators position or orientation is incorrect, adding friction.
Verify that no fuzz has accumulated on the blades, that the rovings are in position. Fuzz indicates the contact between blade and roving is harsh. There may be too much fiction in the system, the blades may be scraping too hard, due to their orientation or surface finish. The graphite may have no sizing on it.
Resin from the top laminates should not drip onto their lower counterparts. If it does, construct channels to redirect its flow.
Soak the wringing system in acetone, and lubricate with wax afterwards (see raw materials). The individual plates are adjusted for a minimum contact with fibers. ( see figure 13).
~ Figure 13: Plan view of the wringing system, showing the roving paths as they exit the bath, pass through the wringer blades, and into the final alignment guides.

.: 18 Not shown is the channel to redirect excess resin in to the bath, as it is extracted from the passing rovings.
Wet Fiber Guidance As shown in figures 4,10,11, and 12, there are guides inside the resin bath for each group of fibers. Cleanse the guides of resin beforehand by soaking them in acetone.
Bolt these to a supporting structure above the resin bath. The fibers are passed through guides in this position, as they are difficult to manipulate once wetted. All parts of the guide in contact with fibers are smooth and rounded.
Pass the groups of rovings through the wringing system, and into the final alignment guides.
Fasten the wet fiber guides to their respective posifions in the bath, at roughly 48" intervals.
Ensure their alignment by pulling the roving groups the final alignment guides. All the roving groups now form straight lines from the creel to the final alignment guides. There are no sharp edges in contact with them.
With all the material in place, except the resin, it is time for a dry run of the fiber pulling system.

Press Operation: Dry Run The dry run establishes that the ravings are aligned with the respesct to the moulds, that all the equipement involved in the manipulation of this materials is in position. The operator must identify all the mechanical components of the press, and verify that they pertorm correctly.
Identification of Double-Pressing Process Components The double pressing process consists of pulling resin soaked rovings through heated mould cavities. Cores are inserted between the upper and lower rovings, the press closes, and laminates are moulded on, using heat and pressure. The process begins with the fiber pulling and holding system.
Fiber pulling and holding system After threading the rovings through the final alignment guides, pass them through the holding station, into the pulley (see figure 14). The holding station serves to hold the rovings in position for the pulley to grab them at the beginning of each cycle. It must maintain the integrity of the alignment in the guides. The pulley has jaws which hold the rovings, without slipping, as it tows them through the mould cavities. With graphite, the velocity should not exceed 80 ft/min, because they are more fragile. The jaws have rack-type serrations clamping onto the wetted rovings, closed with 400 Ibs per laminate.

FIBER HOLDING STATION
HYDRAULIC CYLINDER
WRINGER

l~
" PULLER ~ _ PU~LER 1I
TOP MOULD-~S~OPPd~~ I~ I ~~' II I I~E~EC~ED SHAFT
yV/~EX_IT N~ ~ ~ ~~C
Y-A% S FIBER CLAMPS
BOTTOM MOL
FIBER PULLING MpT(pN HEATER
PIN-JOINT
~'----p INSULATION
--_ Z-AXIS
H-BEAM S R CTU E
x-AXIS
~ Figure 14: Perspective view of pulley and fiber holding station.
After the pull stroke is complete, the lower rovings are clamped into the bottom mould cavity, while the top rovings are supported between the moulds. Otherwise, there would be over 120" of unstable ravings (two lengths of 62" senior shafts) spanning the press.
Unless they are sustained, the wet rovings will oscillate when the pulley stops. The risk is to lose their alignment with respect to the mould cavities.

The importance of roving alignment Figure 15 shows how that the position of the final alignment TOP MOULD

WET FIBERGLASS guides with respect of the ROVINGS

~ ODO mould cavities. The 1L top WET GRAPHITE RAVING

fiberglass ravings are FINAL

ALIGNMENT GUIDE positioned higher than their FAR TOP RAVINGS

graphite counterparts.

FINAL Similarly, the bottom ALIGNMENT GUIDE
~ ~

FGR BUTTUM ROVINGS O O fiberglass ravings ~ 0 are lower ~ than the graphite fibers.
BGTTGM MGULD~
~ Figure lS:Orientation of final alignment guides with respect to mould cavities.
There are several reasons o~ 00 0 why this is important.
Firstly, the roving group GUIDE MAINTAINS must be narrower than the ALIGNMENT DURING
TENSI~NER ~PERATI~N mould cavity to fit inside.
B G T T D M R ~ V I N G S ~ O To bond the laminate to the PNSITIONED IN MGULD ~ ~ O O
C A V I T Y B Y T E N S I ~ N E R , core material, fiberglass '° ' ~ ' and graphite ravings must be separated, because there is no cross-linking between the two materials. So graphite must be in direct contact ~ Figure 16: Insertion of ravings into t~ottom mould cavity.
with the core during pressing, wifhout the interference fiberglass. Figures 16 and 17 show TOP RAVINGS IN
TOP MOULD CAVITY
AS IT IS PRESSED TOWARDS hpyy BOTTOM MOULD.
WD~D CORE
~ Figure 17: Moulds closing on shafts with Correctly alignment ravings.
the final maintain this control. The glass and carbon fibers are compressed separately between the wood and mold surfaces, without any crossover. In addition, the carbon group is the first to encounter the core as the pressing begins Adjusting for Gel Time Mixture Prepare a 100g sample of resin. Mix in 0.3 g of each catalyst, stirring for a uniform colour.
Using a standard soup spoon, pour the catalyzed resin onto an aluminum surface set to the desired mould temperature (100-150°C). Gel time is determining the time it takes the resin to solidify on the hot surface. Rule-of thumb: Probing the resin with a sharp object as it cooks until it no longer yields reveals the gel time. Increasing the percentage of each catalyst decreases the gel time.
The factors influencing the choice of gel time are: Mould temperature, pressure time, resin viscosity, operator dexterity The higher the mould temperature, the shorter the gel time. In addition, the recommended catalysts have a minimum temperature needed to start their role in the reaction. If this is not achieved, the carbon fiber portion of the laminate wilt not be properly cooked. The laminate will have a lower rupture force.
Pressure time is the phase in which the core is pressurized between the iwo laminates. A
higher percentage of catalyst permits shorter pressure time.

A higher concentration of the primary catalyst speeds the chemical reaction, and produces increased viscosity throughout the process. This is useful to reduce the leakage of resin from the moulds during pressing. On the other hand, lower viscosity permits more of it to be wrung out of the laminate, resulting in a lighter end-product.
Finally, a dexterous press operator places four shafts in the mould within 18 seconds, while a less skilled individual can take up to 35 seconds. If the gel time is in this range, parts of the laminate may be hardened before the shaft is pressed, resulting in visible gaps on the finished product For this example, the following configuration is chosen:
Table 1 vinyl tster Kesln 227 Dibenzoyl Peroxide 0.681 0.30%
Trigonox-C 0.1135 0.05%
Mixing the resin with catalysts Using the quantities listed in Table 1, pour vinyl ester resin into one drum of the mixer.
Add the two catalysts, and stir by spinning the propeller at 50-100rpm for 20 minutes.
Pouring Resin into the Bath With the fibers in position, pour resin into the bath directly over the guides. Deviation from this can cause the wetted fibers to twist among themselves. Thus, when the rovings are pulled, they will become entangled, and have to be re-threaded through all the guides. The level is correct when all rovings are completely covered . , 24 Press Operation: First Shafts Final preparations Set the speed of the fiber pulley to 45-50 ft/min.
Coat the mould surfaces with the release compound.
Ensure that the mould temperature corresponds to the desired gel time.
Pull the dry section of the rovings manually until the wetted regions can be gripped by the pulley.
Close the pulley jaws on fibers, ensuring that all rovings are fully clamped.
Description of Press in Loading Position Hydraulic pressure is keeping the press open.
The fiber pulley is positioned next to the final alignment guides.
Jaws of the fiber pulley are open.
Operator loads dry fiber groups in the jaws. The wet portion is now within the wringing system. When clamped, they form straight lines perpendicular to the final alignment guides, and parallel to each other.
The fiber holder is between the pulley and the first mould, closest to the resin bath.
Holding station jaws are open.
Press the start button:
The hydraulic system lifts the press heads out of the way of the pulley.
The mid-point fiber support gets into the ready position.
The ravings are pulled through the press until the end of the stroke.
The top set of ravings is held in place by the pulley, supported by the mid-point guide, and the final alignment guides.
Clamps insert the lower set of rovings into the bottom mould cavities. The wetted rovings begin cooking, and the operator has 15 to 35 seconds to press the shafts.
Beyond this time, they will have hardened so that laminates cannot be formed. exact time available is determined by the gel time of the mixture.
Description of Pulling Motion Operator presses "GO" button Fiber holder retracts out of the way of the pulley.
Mid-point fiber support is positioned to catch the upper fiber groups when the stroke is complete.
Pulley moves through the press as indicated in figure 14.
Pulley reaches end-of stroke station.
Clamps insert the lower roving groups into their mould cavities.
Fiber holder moves into position with its haws open, ready to hold the roving groups.

Core Insertion Insert four cores by the butt ends in to the ejector, which also serves as a locating tool (see the Shaft Insertion section).
Operate the press With both hands safely on the controls, the shaft insertion cylinders sequentially install the cores in the bottom moulds. The mechanism retracts out of the way, and the press closes the top mould cavity on the bottom one, pressing the top roving group onto the core, which in tum is pressed onto the lower roving group. The press remains closed until the resin is fully crystallized. This can take iwo to five minutes, depending upon the recipe (see Adjusting the Gel Time).
Soaking time The pressing cycle immobilizes the rovings within the resin pot for its duration. The mechanical resistance of the graphite laminate increases with the time it spends soaking in resin.
Ejection of Pressed Shafts Upon completion of the pressing cyGe, hydraulics lift the top moulds into their start positions, and the top and bottom ejectors extend. The force fit of the core and mould mean that there is a 50% chance the core will remain in the top or bottom cavity when they separate. Figure 18 shows the end of this process, with the pressed shaft ready for removal.

Feed Rate Fibers are pulled through the pot at variable speed: acceleration from rest to 75 ft/min through the first few inches traveled, maintain high speed for the length of the molds, then deceleration to rest in the final inches.
Fiber Tensioning System Inserts the bottom laminates into the mold cavities and maintains tension for the first minute of pressing. When under tension, guides at exit of the wringing system maintain the carbon in the center of each mold cavity, with a fiberglass on in each comer.
Tension is introduced to the top laminates by the closure of the press. The top mold cavities lowered towards the top laminates, held in position by the pulley jaws, an intermediate support, and fiction in the wringing system.
Shaft insertion Non-laminated hockey shafts placed manually into the ejector at the butt end.
The butt INSERTION C RR A E
~.-~ =~------ ~ caRE
INSERTION CYLINDER ~ TAPER
~ ~~EJECTNR/C~RE LNCAT1NG TNOL
~ Figure 19: Wood shaft sequential insertion system.

ends are oriented towards each other longitudinally. The ejector profile is larger than the shaft width, so it serves as locating tool, ensuring that the portion of core inserted here is true to the mould cavities. The tapered profile of the mould holds the shaft in position.
Vertical downward forces are applied and maintained in sequence every 4 to 13 inches of shaft length, depending upon the crookedness of the shaft. Figure 18 shows the sequential nature of the shaft insertion system. The cylinder closest over the ejector descends first, ensuring that this section of the core is true with respect to the mould cavities. Wood cores are naturally crooked. Figure 19 shows an exaggeration of a crooked core in the mold. The distance between the insertion cylinders determines how crooked the core can be. For example, a given core will have much less deviation over a length of 6" than 24".
~ Figure 20: Exaggeration of crooked wood core in the mould.

. r .. 28 T ' Mould Technology Single pressing technology has only one laminate, in the bottom of the mould cavity. This allows the mould cavity to be much deeper, with a more gradual entry. There is a larger lateral contact area to force the core to be true to the mould. In addition, it is pressed by a flat surface. In double pressing, the upper cavity can trap the core in a position where it is not parallel to the cavity surfaces. Figure 20 compares single and double pressing moulds.
In double pressing, the profile of the mold has is composed of an entry radius followed by a reversed radius which horizontally compresses the shaft core, sealing in the excess resin. Flat regions of the profile tapered for further compression as the core descends into the mold.
The width of the entrance is equal to the largest shaft width. 47 to 50% of the core depth covered by the mold.